An embodiment of the present invention relates to a method for aligning a phase retardation plate with a display panel.
Stereoscopic display has become a key trend in today's display industry. Generally speaking, a 3D image is created by application of parallax principles, wherein the left eye of a viewer receives only a left-eye image and his/her right eye receives only a right-eye image. Here, the left-eye and right-eye images are a pair of stereoscopic images with a parallax.
Serial I/O mode is one of the ways to achieve stereoscopic images, wherein at a first moment, a left-eye image is provided and can be seen only by the left eye of a viewer, and at a second moment, a right-eye image is provided and can be seen only by the right eye. Due to the retinal afterimage, the viewer feels like see both the left-image and right-eye image at the second frame, thus resulting in a three-dimensional image in the viewer's brain.
Parallel I/O mode is another way to achieve stereoscopic images, wherein at the same frame, a part of pixels are set to display a right-eye image and another part of pixels to display a left-eye image. By using a grating or polarized glasses, the right-eye image can be seen only by the right eye of a viewer, and the left-eye image can be seen only by the left eye, hence resulting in a three-dimensional image in the viewer's brain.
Stereoscopic image display device using polarized glasses has become a mainstream technology in today's display industry, wherein a phase retardation plate is provided at the front surface of a display panel, so as to adjust the polarization direction of emitted light. The phase retardation plate can be a risen phase retardation plate or a liquid crystal cell, or any other components for adjusting the polarization direction of light emitted from different parts of pixels. FIG. 1 is a schematic diagram of the principle of an existing 3D display technology. As shown in FIG. 1, there are, in front of the viewer, from the distant to the near, a display panel 10, a phase retardation plate 20, an emitted image 30, and a pair of polarized glasses 40. Left-eye images L and right-eye images R are displayed alternately on display panel 10. The phase retardation plate 20 is provided at the front surface of the display panel 10. Strip-shaped regions with phase retardation of λ/2 (λ is the wavelength) and zero alternately are provided on the phase retardation plate 20. In this way, the polarizing direction of light emitted from the pixels in places corresponding to the λ/2 phase retardation regions will be rotated by 90 degrees. As a result, when a viewer wears the glasses 40 which contains a pair of polarizing filters with orthogonal polarization directions, light emitted from left-eye pixels is allowed only to be seen by the left eye, and light emitted from right-eye pixels is allowed only to be seen by the right eye, hence experiencing a 3D display image. Optionally, λ/4 phase retardation regions and −λ/4 phase retardation regions can be alternately provided on a phase retardation plate, so as to produce left-handed and right-handed circularly polarized light. In this case, a viewer can see a 3D image with glasses containing different circular polarizing filters (not shown in FIG. 1).
In the above-described 3D display technology, it is of vital importance to align the phase retardation plate 20 with the display panel 10. If any large misalignments exist, light emitted from left-eye pixels is for example turned into polarized light with orthogonal or opposite polarization directions after passing the phase retardation plate 20, resulting the left-eye images can be seen by both eyes. More severely, the left-eye images can only be seen by the right eye, while the right-eye images can only be seen by the left eye, resulting in serious image crosstalk and failure of creating a 3D image.
In an existing method of aligning an array substrate with a color filter substrate, four pairs of alignment marks, which can be detected by a image pickup device such as CCD image sensor, are provided on the four corners of both the array substrate and color filter substrate respectively, so as to assure the accuracy of the alignment. Since the alignment marks are formed of a colored metal or a black matrix (BM) mask, it is quite easy for a CCD image sensor to detect them. However, since in current stereoscopic display technology, oriented liquid crystal layer, for example, is often used as a phase retardation plate, it is improbable for an ordinary CCD image sensor to detect the structural information of the phase retardation plate, and as a result, impossible to align the phase retardation plate and a display panel in the way described as above. In an existing technology, the alignment of a phase retardation plate and a display panel can also be done manually, that is, the relative positions of a phase retardation plate and a display panel can be determined by a person's eyes, depending on his/her opinion on whether the 3D display effect is satisfactory or not. In addition, the screen also needs to be lightened up during the process. Therefore, such a manual alignment method is rather inefficient and inaccurate. It is necessary to develop, according to features of the products and display requirements, a new alignment method with enhanced accuracy and efficiency.